During transform-based video compression processing, motion vectors, which are identified during motion estimation and then used during motion-compensated inter-frame differencing, are constrained to coincide with block boundaries in the reference data. Block-based motion vectors have components that correspond to integer multiples of block dimensions. For example, for (8.times.8) blocks, allowable motion vector components are ( . . . , -16, -8, 0, +8, +16, . . . ). Constraining motion vectors in this way enables the resulting encoded video bitstream to be further processed in the transform domain without having to apply inverse and forward transforms. In particular, an existing input bitstream is partially decoded to recover the motion vectors and prediction error (i.e., dequantized transform coefficients). Because the motion vectors coincide with block boundaries in the corresponding reference data, motion-compensated inter-frame addition can then performed in the transform domain to generate transform data for subsequent processing (which may ultimately involve re-encoding the transform data into another encoded video bitstream). Because motion compensation can be performed in the transform domain, the bitstream data can be further processed in the transform domain and without having to apply expensive and lossy inverse and forward transforms.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of the filing date of U.S. provisional application No. 60/102,214, filed on Sep. 29, 1998.
An information insertion/detection system for detecting and inserting DCT coefficients in image signals includes a resolution analyzer for receiving image code data and outputting the image code data and image size information of the image code data, an insertion pattern determining unit for receiving the image code data and the image size information and outputting the image code data and pattern information, an information inserter for receiving the image code data and the pattern information and producing image code data by inserting information of the DCT coefficients into the image code data and a video analyzer for receiving the image code data and producing information of insertion strength of the DCT coefficients. The information is inserted in DCT coefficients so that the information can be detected by referring to an image size of MPEG data inputted to the system when the image data is converted into a reference image size.
A coded object-based picture signal representing a picture is transcoded to a coded block-based picture signal representing the picture by culling signal portions that represent objects not visible in the picture from the coded object-based picture signal to generate a culled object-based picture signal. Portions of the culled object-based picture signal are partially decoded and from them are generated blocks of a partially-coded block-based picture signal in which the blocks have different coding states. Finally, the blocks of the partially-coded block-based picture signal are re-encoded to generate the coded block-based picture signal in which the blocks have a uniform coding state.
A transcoding apparatus converts first coded data obtained from a plurality of frames forming a video image by means of a coding algorithms including an interframe prediction coding algorithm with motion compensation into second coded data having a different structure. More specifically, the transcoding apparatus takes a portion of frames which have had the interframe prediction coding and are included in the plurality of frames forming the video image as processing object frames, and from at least the first coded data corresponding to the processing object frames, generates the second coded data corresponding to coded data which are to be obtained when performing the interframe prediction coding on the processing object frames with reference to second reference frames which are different from first reference frames referenced in the interframe prediction coding of the processing object frames. In order to the second coded data, the transcoding apparatus has a motion information calculating portion for calculating motion information to be included in the second coded data using at least motion information contained in said processing object data.
A method and apparatus are disclosed by which a translucent logo is inserted into the transcoded digital bitstream of an MPEG transcoder without changing the digital nature of the bitstream. Such an MPEG transcoder has cascaded decoding and encoding sections. A translucent logo is generated and is added to the reconstructed video image produced by the decoder section of the MPEG transcoder upstream of the transcoder's encoding section. The encoding section of the transcoder then encodes the bitstream which includes the translucent logo.
A transcoding method for inserting a visual element into an encoded bit stream with minimal decoding of the encoded bit stream. The transcoding method includes the steps of receiving an encoded bit stream containing a picture, partially decoding a copy of the bit stream, determining if a segment of the picture in the bit stream is affected by the insertion of the visual element, re-encoding the segment if the segment is affected by the insertion of the visual element, and outputting the re-encoded bit stream. The encoded and re-encoded bit streams may be MPEG-encoded bit streams. The re-encoded bit stream may be output using a bit rate control process that randomly selects an initial processing point within the re-encoded bit stream, requantizes the re-encoded bit stream using a modified quantization table, and/or utilizes a slice-level stopping criteria for selectively starting or ending bit rate control.
